Whether an organization’s attempts to influence legislation, i.e., lobbying, constitute a substantial part of its overall activities is determined on the basis of all the pertinent facts and circumstances in each case. The IRS considers a variety of factors, including the time devoted (by both compensated and volunteer workers) and the expenditures devoted by the organization to the activity, when determining whether the lobbying activity is substantial.
Under the substantial part test, an organization that conducts excessive lobbying in any taxable year may lose its tax-exempt status, resulting in all of its income being subject to tax. In addition, section 501(c)(3) organizations that lose their tax-exempt status due to excessive lobbying, other than churches and private foundations, are subject to an excise tax equal to five percent of their lobbying expenditures for the year in which they cease to qualify for exemption.
Further, a tax equal to five percent of the lobbying expenditures for the year may be imposed against organization managers, jointly and severally, who agree to the making of such expenditures knowing that the expenditures would likely result in the loss of tax-exempt status.
Private foundations are subject to a different set of taxes on their lobbying expenditures; churches are not subject to excise taxes on excessive lobbying.
Schedule C, Form 990, Political Campaign and Lobbying Activities